Apparatus for obtaining interior ballistics data



S. GOLDEN June 22, 1954 APPARATUS FOR OBTAINING INTERIOR BALLISTICS DATAFiled Dec. 11 1950 have constituted primary data for `ary photographicplate, lm or paper. "values noted above may then be determined byPatented June 22, 1954 APPARATUS FOR OBTAINING INTERIOR 4 BALLISTICSDATA Sidney Golden, Forest Hills, N. Y., assigner to the United Statesof America as represented by the Secretary of the Army ApplicationDecember 11, 1950, Serial No. 200,210

This invention relates to apparatus for obtain- Heretofore, the study ofinterior ballistics has included the recording of the pressures within apropellant chambervvith` respect to the elapsed time of burning of thepropellant. Such records have been obtained as a series of pictures onphotographic paper or film mounted on a rotating drum. The pressure-timecurves thus obtained interior ballistics work. Values useful in thestudy of interior ballistics include maximum pressure, average pressure,pressure integrated with re- "spect to time, apparent burning time, andaction 1 time. These values have been obtained from the above-mentionedpressure-time curves by linear measurements and by integration with theuse of a planmeter.

In order to give detailed consideration to the i interior ballistics ofparticular ordnance,A it is desirable to obtain a combined record ofpressures, integrated pressure and time on a station- All the inspectionand measurements of a single record. All the desired values may bequickly noted from the combined record by simple linear measurements anda minimum of computations.

It is therefore the object of this invention to provide an apparatus forobtaining a combined record indicating the pressures, the pressureintegrated with respect to time and the time of burning of an ordnancepropellant.

It is the further object of this invention to provide an apparatus forobtaining a single photographic record of interior ballistics datarelating to the burning of ordnance propellants.

It is a further object of this invention to provide an electronicapparatus which permits the visual observation of the pressures,pressures integrated, with respect to time and the time of a propellantburning process in order that erratic performance may be immediatelynoted.

It is another object of this invention to provide an improved method ofobtaining interior ballistics data including pressure integrated withrespect to time.

Other objects and advantages of the invention will be readily apparentfrom the following de- 2 Claims. (Cl. 7S-35) 2 scription of theaccompanying drawings in which:

Fig. 1 is a diagram of a preferred form of apparatus according to thepresent invention.

Fig. 2 is an enlarged diagrammatic view of a combined record of interiorballistics data of the general type obtained by the method and apparatusof the invention.

With reference to Fig. l for purposes of illustration, numeral l0indicates a chamber within which the propellant charge is burned. Thechamber I0 may be the motor of rocket type ordnance provided with anozzle I2 for the escape of combustion gases, or it may be the closedpropellant chamber of a gun. Associated with the chamber l0 is a straingage measuring circuit, indicated generally at i4, which comprises inits simplest form a resistance I6, a battery I8, and a xed resistance20. Resistance I6 is mounted so that its resistance to current frombattery i8 will vary with changes in pressure within chamber I0. Thepotential appearing at terminals 22 `has therefore a magnitude which isa function of the pressures produced' by burning the propellant chargewithin chamber I0. This potential resulting at terminals 22 is amplifiedin a `suitable amplier 24 and then applied to the vertically deiiectingplates 26 of a cathode ray oscilloscope 28. The potential acrossterminals 22 is also connected to an integrating circuit 30. a suitableform of which is shown as comprising a resistance 32 and a condenser 34.The potential at output terminals 36 of the integrating circuit 30 willhave a magnitude which is a function of the pressures Within chamber I0integrated with respect to time. The potential at fterminals 36 isconnected to a suitable amplier 38 and thence to the horizontallydcflecting 'plates 40 of the oscilloscope 23. The amplifiers 24 and 38and the cathode ray oscilloscope 2'8 may be of conventional character,equipped with the usual control and adjustment devices. A timing pulsegenerator 42 is connected to the grid 44 of oscilloscope 28 toperiodically vary the intensity of the cathode ray produced. The pulsegenerator 42 may also be of conventional character and may include atuning fork oscillator to control the generation of pulses at a desiredrate, such as at intervals of 0.01 second. The oscilloscope 28 isequipped with the usual screen on which the deflections of the ray maybe observed and/or photographieally recorded by a suitable camera 46.

The method of operation of the apparatus illustrated will now bedescribed. The ampliers 2B and 38 are adjusted to locate the cathode rayof oscilloscope 28 at a desired zero or point of orig-in, for example asshown at 48 in Fig. 2.

Where the interior ballistics data is to be photoduce a horizontal trace5A ataknown pressure,` such as 10,000 pounds per square inch.

calibration is eiected by applying a known potential corresponding to aknown pressure tothe vertically deflecting platesii'' ofthe'oscil-lo'scope,` and may be done for more than one pressure. Theapparatus is then ready tc indicate and/or record the pressure,integrated pressure and time of the burning of a propellant chargeinthe^ chamber i0. The propeilant charge is ignited by conventionalignition' means.` As 'the pressure Within chamber i0 rises, the cathoderay of. foscilloscope' 23 .moves ups/ard lfrom the point of originf148.- The vertical distance measuredv on axis 50 indicates the pressurewithin chamberV i0 at.v any-given instant; The horizontal distancemeasured'on-axis 52 indicates integrated pressure with respect to timeat anygiveninstant; The dots or spots 55 along the pressure-:integratedpressurecurvew' indicatethe passage of known units of time afterthe'ignition of the propellant charge.` Hence the number of spots 50from the point of originl to the apparent end of burning indicates'theapparent burningtirne; The maximum pressure.producedV during" burning.is indicated'by the maximum pressure ordinate of the curve v 5S measuredon the vertical axis 50. The average pressure from the beg-inning ofthepres.- sureffrise -to any-point during therburning` of thechargezmayrbe determined: by .dividing .theintegra-tedlpressure: atVthatpoint` byithe' elapsed timerfromthe point of origin 48 lto lthegivenV point. The average rate of changeof pressure with yrespect totime at a given point may Ybe determinedfby findingy thefchange inVpressure between twoitiming impulses 50 and: dividingby the interval'oftime corresponding to the timingrim.- pulses. The instantaneous value ofther-ate'. of change of pressure withv respect to timeV may bedetermined .b5/,measuring the slopeof the curve .i

5ft-at thepoint `and' multiplying this quantity by the-pressure at thatpoint.

The-.method andv apparatus disclosed therein forpbtaining interior`ballistics data has the following advantages.. formatinn dealing withballisticv performanceais obtained with'linear measurements of a singlerecord;` No' synchronisml of the camera taking tbefrecord- Yoi the eventis necessary since.` the sweep of-the cathoderay on the loscilloscopescreen depends on theintegrated pressure which remains zero until theburning of thepropellant begins.l Stationary iilm recording cameras maybe-used, eliminating the need for expensive drum cameras'with undulylong records for developing and-handling. By visually observing theoscilloscopefduring the burning of the propellant charge, the operatorcanl seev the pressuredn'- The most pertinent s tegrated pressure curvetraced out onthe screen and can detect erratic performance by the timethe burning is completed. Since a stationary recording film is used,auxiliary information such Y as the round number, ignition delay, andthe like may readily be recorded simultaneously on the lm record.

Other advantages and numerous modications of this invention will bereadily apparent to those `skilled in the art. The bounds of myinvention aredenedbythe spirit and scope of the followingiclaims.

I claim:

1. In'anA apparatus for obtaining a combined pressure', pressure`integrated with respect to time', andtime` record of conditions duringthe burningfofl an ordnance propellant within a chamber, the combinationcomprising a cathode rayoscilloscope havinga pair of vertically and apair of horizontally deecting plates, means for deriving-an eiectricalvpotentiallzhaving a magnitude-which is a function of the'presresureswithin said chamber, meansfor applying said potential to one ofsaid pairs of defleeting plates, means for iniegratingsaid potentialwith respect to time and deriving a' second electrical potential havingla magnitude which is a. function of said pressures integrated with`respectito time, means for applyingsaid latter potential to the other ofsaid pairs of `defl'ecting:platesf,-and means for periodically varying:the: intensity of the cathode ray at predetermined time'intervals.

2. In 'an apparatus for obtaining a photo..i graphie. record of thepressure, pressurezinte- :grated with respect to time, and time Vofcondi'- tions during the burning of an` ordnance propel?- lant within achamber,v the combinationncomprisiig a cathode rayoscilloscopelhavingia: pair of vertically and a pair of horizontallydeilecting plates, means for derivingan electricalrpotental having amagnitude which is a function of the pressures within'saidchamber, meansfor. apply'- ing'said potential to one of said pairs of deflectingplates, means for integrating said potential with respect to timeandderiving a secondfpot'ential? having ay magnitude which is a fun'ctioniof said'` pressures integrated with respect' to time, means forVapplying saidlatter potential' to the other of said pairs of deflectingplates; means for-periodically varying the intensity of" `the' cathoderay at predetermined time intervals, and mea-ns for photographicallyrecording' the trace `ofthe cathoderay across the screen of saidoscilloscope.

References Citedrin the; file of thisypatent;VY

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